Dialysis control system and method

ABSTRACT

Method and apparatus for extracorporeally dialyzing the blood of a patient with only a single venipuncture including withdrawing blood from the patient through the venipuncture and forcing the blood along an arterial path to a dialyzer. Blood emerging from the dialyzer is then conducted along a venous path again to the patient. The pressure is monitored in the extracorporeal system to trigger occluding devices which alternately open and close the arterial and venous paths, the closure time being asynchronous so that undialyzed blood is taken from the patient at a flow rate which differs measurably from the flow rate that dialyzed blood is injected into the patient.

Sites tet 1191 PP Aug. 20, 1974 DIALYSIS CONTROL SYSTEM AND 3,416,66412/1968 Kumme et a1. 210/321 x METHQD 3,731,680 5/1973 Wright et al.128/214 F Inventor: Klaus F. Kopp, Kirchseeon,

Germany Vital Assists, Inc., Salt Lake City, Utah Filed: Apr. 16, 1973Appl. No.: 351,720

Related US. Application Data Continuation-impart of Ser. No. 149,905,June 4, 1971, Pat. No. 3,756,234.

Assignee:

References Cited 1 UNITED STATES PATENTS 10/1955 Melrose 128/DIG. 3

OTHER PUBLICATIONS Twiss Lancet November, 1964, No. 7369 (p. 1106).

Primary ExaminerDalton L. Truluck Attorney, Agent, or FirmI-l. RossWorkman [5 7 ABSTRACT Method and apparatus for extracorporeallydialyzing the blood of a patient with only a single venipunctureincluding withdrawing blood from the patient through the venipunctureand forcing the blood along an arterial path to a dialyzer. Bloodemerging from the dialyzer is then conducted along a venous path againto the patient. The pressure is monitored in the extracorporeal systemto trigger occluding devices which alternately open and close thearterial and venous paths, the closure time being asynchronous so thatundialyzed blood is taken from the patient at a flow rate which differsmeasurably from the flow rate that dialyzed blood is injected into thepatient.

4 Claims, 1 Drawing Figure DIALYSIS CONTROL SYSTEM AND METHOD Thisapplication is a continuation-in-part of my copending application Ser.No. 149,905, filed June 4, 1971, now US. Pat. No. 3,756,234 issued Sept.4, 1973.

BACKGROUND remarkably improved by increasing the stroke volume of thedialyzing system. Stroke volume is herein defined as the blood flow rate(ml/min) divided by the number of cycles per minute of the flow controlsystem. Increased stroke volume increases efficiency because it reducesthe admixing so common in single-fistula dialy- SIS.

Prior art systems have commonly employed pressure monitors ortime-controlled clamps to control the flow of blood out of the patientinto a dialyzer and then from the dialyzer into the patient again.conventionally, care has been taken to assure that the blood flow rateout of the patient was essentially equal to the blood flow rate in thereturn line. Wherever the flow rate in the arterial line (away from thepatient) and the venous line (toward the patient) are the same, thestroke volume cannot be maximized. This will be understood byrecognizing that increase in blood flow rate according to the knownprior art also requires a corresponding increase in cycles per minute ofthe flow control system.

BRIEF DESCRIPTION AND OBJECTS OF THE INVENTION The present invention,including novel method and apparatus, reduces patient trauma and tissuedamage by accommodating extracorporeal hemodialysis by providing forvariations in stroke volume to maximize the efficiency of hemodialysis.While this invention may have application in a variety of extracorporealsystems, it presently appears most significantly advantageous indialysis through a single venipuncture. Generally, once the venipuncturehas been performed, blood is conducted away from thevenipuncture sitethrough the arterial branch of a bifurcated blood path at a pressurewhich is low enough to prevent collapsing the arterial branch or thepatients blood vessel. The bifurcation is located next to the needleconnector to keep the resulting deadspace as small as possible. Theblood is then forced to the extracorporeal hemodialyzer under pressurewhile the venous branch is occluded. Thereafter, the venous branch ofthe bifurcated flow path is opened for a predetermined time to returnblood again to the venipuncture site. The time of the return in thevenous branch is controlled so that the return flow rate differs fromthe flow rate in the arterial branch. The method using the singlevenipuncture is made possible by alternating the blood flow into and outof the patient at the venipuncture site. A unidirectional pulsatileblood flow through the dialyzer is established by, for example, drawingthe blood from the patient at a pressure which will not collapse thepatients blood vessel or arterial branch. In the interim, the venousbranch is occluded so that substantial pressures are developed in thedialyzer. In a preferred example, at a predetermined pressure limit, thevenous occlusion is opened for a predetermined time, allowing the bloodto return to the patient at a flow rate substantially greater than therate of withdrawal.

It is, therefore, a primary object of the present invention to providean improved method of extracorporeal hemodialysis.

It is another primary object of the present invention to provideimproved apparatus facilitating extracorporeal hemodialysis with asingle venipuncture.

Another valuable object of the present invention is to provide animproved system for single needle dialysis for providiing variablestroke volume to improve the efficiency of an extracorporeal dialyzer.

One still further and no less important object of the present inventionis to provide a novel method of varying the blood flow rate in thevenous branch of an extracorporeal system with respect to the flow ratein the arterial branch.

These and other objects and features of the present junction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The FIGURE is a schematic perspectiveillustration of a presently preferred system for dialyzing a patientsblood using a single venipuncture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is now madeto the preferred embodiments of the invention .as'illustrated in theFIGURE. A hollow cannula 24 is adapted to be situated within a bloodvessel of a'patient. Preferably, the cannula has been placed accordingto any suitable technique such as venipuncture. The cannula 24 may be ofany suitable type and may be made of any desirable material such asradiopaque Teflon. One suitable cannula has been found to be theAngiocath intravenous placement unit manufactured by DeseretPharmaceutical Company, Inc., Sandy, Utah. A 14 -gauge catheter having alength of between 1 and .2 inches has been found to be most effective.Nevertheless, it is also presently preferred to use a hollow needle orany other suitable hollow instrument which can be effectively placedwithin a vein. In this specification, cannula means any hollow tubingwhich can be placed in a patients blood vessel.

In the illustrated embodiment, the cannula 24 is bifurcated at coupling28. Coupling 28 has an arterial branch 30 and a venous branch 32,arterial branch 30 being attached in conventional manner to a rubber orplastic tube 34. Tube 34 will hereinafter be referred to as the arterialline 34.

Arterial line 34 is situated over the face 36 of a blood pump generallydesignated 38. Blood pump 38 is conventional and normally includes arotatable shaft 40 upon which is mounted a transverse bar 42. The bar42,has, at its respective ends 44 and 46, rotatable cylinders 48 and 50.

Approximately one-half of the circular path traversed by the cylinders48 and 50 is bordered by a semi-circular track 52. The arterial line 34is caused to follow the inside surface 54 of the track 52. Thus, as thecylinders 48 and 50 traverse their circular path about the axis of shaft40, the arterial line 34 will be squeezed between the respectivecylinders and the track 52. Conventionally, the bar 42 rotates clockwisearound the shaft 40 so that the squeezed portion of the arterial line 34isdeveloped between the cylinder and the track 52 at the leading end 56of the track and progresses over the entire inside surface 54 of thetrack to the trailing end 58 thereof. As the squeezed portion of thearterial line 34 progresses over the inside surface of the track 52,blood in the arterial line 34 is forced to the dialyzer generallydesignated 60. It can be appreciated that when the cylinder 48 reachesthe trailing end 58 of the track 52, the cylinder 50 will engage thearterial line 34 at the leading end 56 so that a constant forwardpressure is exerted on the blood to move from the blood vessel 22 to thedialyzer 60 as long as the pump is in operation.

Any suitable conventional dialyzer can be used with the present system.An example of one suitable dialyzer which could be used is described inUS. Pat. No. 3,723,305 and manufactured by Vital Assists, Inc. of SaltLake City, Utah. Another suitable dialyzer is the Coil EX-Olmanufactured by Extracorporeal, Inc. Blood emerges from the dialyzer 60in the venous line 62 which is attached in a conventional way to thebranch 32 of the coupling 28. Preferably, a bubble trap 64 is interposedin the venous line 62 to prevent bubbles from passing through thecannula 24 into the blood vessel 22. The bubble trap 64 may be anysuitable conventional bubble trap such as that used with blood infusionapparatus.

A pressure conductor 66 is connected into the venous line, preferably atthe bubble trap 64 above the surface level 68 of the blood. Thus,pressure within the bubble trap 64 and venous line 62 can be transmittedthrough the conductor 66 to a controller generally designated 70. Thecontroller 70 includes (a) a pressure monitor which may be of anysuitable type such as is manufactured by Cambridge InstrumentCorporation of Great Britain, and (b) a time circuit which may be of anysuitable type such as is manufactured by Eagle Signal Company, aDivision of E. W. Bliss Co. of Davenport, Iowa.

The controller 70 has a calibrated bezel 82 with indicia thereonrepresenting, for example, millimeters of mercury. An indicator 84 iscontrolled by venous line pressure in conductor 66 so that when thevenous line pressure in conductor 66 rises, the indicator 84 rises toindicate the pressure in millimeters of mercury (mm Hg). Similarly, whenthe pressure in conductor 66 drops, the indicator 84 drops to representthe decreasing pressure in millimeters of mercury. A manually adjustableset point is determined by the position of marker 88. For example,marker 88 sets the upper limit of blood pressure in the venous line 62as will now be more fully described.

The set point 88 represents a pressure maximum in the venous line 62which, when reached, actautes clamp 150 to open the venous line 62 andclose the arterial line 34 as will be hereinafter more fully described.Venous line 62 will again be closed after the expiration of apredetermined time increment. The

time increment is determined by positioning dial 86 on the controller70. Although any suitable time range could be included, incrementsbetween 0.5 second and 1.5 seconds have been found adequate for mostsignal fistula systems.

In the illustrated embodiment, a double clamp 150 is provided. The clamp150 has intersecting channels 152 and 154 through which the venous andarterial lines 62 and 34, respectively, pass. The clamp 150 hasa detent156 situated between the channels 152 and 154, the detent 156 beingselectively actuated alternately into channel 152 or 154 to occlude andclamp off the arterial and venous lines. Control of the detent isprovided through electrical conductors 160 and 162 connecting the clamp150 to the controller 70.

The Method Initially, the set point on the controller is adjusted bymoving the marker 88 to represent the desired venous pressure. Thearterial and venous lines are primed by filling the lines with isotonicsaline. When a single venipuncture or cannulation has been performed,the saline in the arterial and venous lines 34 and 62 is replaced withblood.

The pump 38 operates continuously to force blood toward the dialyzer 60.The speed of the blood pump is selected to be at a maximum rate whichwill not collapse the arterial line 34 of the patients blood vessel.

Assuming that the venous line 62 is occluded by clamp 150, blood iswithdrawn from the patients blood vessel 22 through the cannula 24 andarterial line 34 into the dialyzer 60. Continued pumping by the pump 38causes the pressure in the venous line 62 to increase because of theocclusion of the venous line in the channel 152. As the pressure rises,the indicator 84 will rise to the set point determined by marker 88.When the set point is reached, clamp will be actuated to open the venousline 62 and to occlude, essentially simultaneously, the arterial line34.

Importantly, the arterial line 34 is occluded for a predetermined timeincrement which is selected at dial 86 to be just long enough to reducevenous pressure by injecting blood into the patient through the cannula24. It has been found that the time required to return a quantity ofblood through the venous line to the patient is proportional to thepressure developed on the blood in the venous trap 64. Accordingly,higher pressure settings by marker 88 accommodate shorter timeincrements for opening the venous ine. According to this embodiment ofthe invention, it is presently preferred that the time increment duringwhich the venous line is open be less than the time increment duringwhich the venous line is closed. In a preferred embodiment, for example,the open time of the arterial line compared to the venous line wasadvantageously maintained in a ratio of 2:1. The flow rate through thevenous line to the patient will depend upon the pressure developed inthe venous trap 64 while the line is occluded.

While the above described embodiment emphasizes the value of improving ahigh pressure dialysis system by developing greater flow in the venousline 62 than the arterial line 34, it is sometimes desirable to maintainvery low pressures in the dialyzer 60. In that circumstance, it is moredesirable that the velocity of the outflow blood through the arterialline 34 be greater than through the venous line 62. This can be easilyacbe selecting a greater time increment on dial 86 to, for

example, up to as much as several seconds, allowing the blood to returnmore slowly. The small pressure gradient in the venous line 62 resultingfrom the low pressure dialyzer will assure that the blood return flowrate is less than the blood withdrawal flow rate.

It is observed that the speed of pump 38 should be controlled so thatblood 18 is not withdrawn so quickly from the patient that the arterialline or the patients vein collapses. However, a'greater blood returnflow rate incurs no risk of collapse of the venous line or the patientsvein and the greater flow rate return is advantageous to maximize theefficiency of the system.

From the foregoing, it can be appreciated that improved dialysis of apatients blood can be obtained with a single venipuncture where thestroke volume is increased by withdrawing blood from the patient at aforms without departing from its spirit or essential characteristics.The described embodiments are to be considered in all respects only asillustrative and not restrictive and the scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed and desired to be secured by United States LettersPatent is:

1. A method of dialyzing the blood of a patient in an extracorporealhemodialyzer, the steps of:

cannulating a blood vessel of a patient with a single hollow cannula,the cannula being bifurcated extracorporeally into an arterial branchand a venous branch, the hemodialyzer being situated therebetween;closing the venous branch for a first variable time increment andsimultaneously aspirating blood out of the patient blood vessel throughthe arterial branch toward the dialyzer until blood in the venous branchreaches a predetermined elevated pressure;

closing the arterial branch and opening the venous branch for a secondpredetermined time increment, the second time increment being less thanthe first, so that the elevated pressure causes the blood in the venousline to be conducted to the patient at a flow rate which is greater thanthe rate at which the same quantity of blood is withdrawn from thepatient.

2. A method of controlling an extracorporeal hemodialysis sytemcomprising an arterial line conducting blood away from a patient, avenous line conducting blood toward the patient, a dialyzer situatedbetween the arterial and venous lines and a blood pump forunidirectionally displacing the blood, the steps of:

aspirating blood from the patient through the arterial line at a flowrate which will not collapse bloodconducting conduit;

closing the venous line while continuing to aspirate the blood until apredetermined elevated pressure is reached in the venous line;

thereafter opening the venous line and essentially simultaneouslyclosing the arterial line for a predetermined time increment to injectthe blood under pressure into the patient; and

insuring that the duration of a venous line opening is less than theduration of the arterial line opening.

3. A system for controlling the dialysis of blood comprising an arterialline conducting blood away from a patient, a venous line conductingblood toward the patient, and a dialyzer situated between the arterialline and venous line, the improvement comprising:

means for pumping blood unidirectionally from the patient through theopen arterial line at a pressure which will not collapseblood-conducting conduit;

means for closing the venous line while the blood is being pumped untila predetermined elevated blood pressure is reached in the venous line,said closing means comprising pressure-responsive control meansadjustable to maintain the closure of the venous line independent oftime;

means for opening the venous line and essentially simultaneously closingthe arterial line, said opening means comprising time-responsive controlmeans adjustable to maintain the venous line open independent ofpressure in the line for a predetermined time increment to inject theblood under pressure to the patient, the duration of the closure of thearterial line being less than the duration of the venous line closure.

4. A system for controlling the dialysis of blood comprising an arterialline conducting blood away from a patient, a venous line conductingblood toward the patient, and a dialyzer situated between the arterialline and the venous line, the improvement comprising:

means for pumping blood unidirectionally from the patient through theopen arterial line at a pressure which will not collapseblood-conducting conduit;

duration of the venous line closure.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,830,234 Dated August 20, 1974 Inventor(s) KLAUS F. KOPP It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, line 63, "actautes" should be -actuates--; Column 4, line 4,"signal" should be ---single--;

Column 4, line 49, "ine" should be --line--;

Column 5, line 2, "be" should be --by-- Signed and sealed this 29th dayof October 1974.

(SEAL) Attest:

' McCOY M. mason JR c. MARSHALL DANN Attesting Officer Cormnissioner ofPatents FORM Po-105o (10-69) I I UsCOMM-DC 60376-P69 I Q U. S,GOVIINMEIIT PR NTING OPTIC! "I, 0-3l-J3l

1. A method of dialyzing the blood of a patient in an extracorporealhemodialyzer, the steps of: cannulating a blood vessel of a patient witha single hollow cannula, the cannula being bifurcated extracorporeallyinto an arterial branch and a venous branch, the hemodialyzer beingsituated therebetween; closing the venous branch for a first variabletime increment and simultaneously aspirating blood out of the patientblood vessel through the arterial branch toward the dialyzer until bloodin the venous branch reaches a predetermined elevated pressure; closingthe arterial branch and opening the venous branch for a secondpredetermined time increment, the second time increment being less thanthe first, so that the elevated pressure causes the blood in the venousline to be conducted to the patient at a flow rate which is greater thanthe rate at which the same quantity of blood is withdrawn from thepatient.
 2. A method of controlling an extracorporeal hemodialysis sytemcomprising an arterial line conducting blood away from a patient, avenous line conducting blood toward the patient, a dialyzer situatedbetween the arterial and venous lines and a blood pump forunidirectionally displacing the blood, the steps of: aspirating bloodfrom the patient through the arterial line at a flow rate which will notcollapse blood-conducting conduit; closing the venous line whilecontinuing to aspirate the blood until a predetermined elevated pressureis reached in the venous line; thereafter opening the venous line andessentially simultaneously closing the arterial line for a predeterminedtime increment to inject the blood under pressure into the patient; andinsuring that the duration of a venous line opening is less than theduration of the arterial line opening.
 3. A system for controlling thedialysis of blood comprising an arterial line conducting blood away froma patient, a venous line conducting blood toward the patient, and adialyzer situated between the arterial line and venous line, theimprovement comprising: means for pumping blood unidirectionally fromthe patient through the open arterial line at a pressure which will notcollapse blood-conducting conduit; means for closing the venous linewhile the blood is being pumped until a predetermined elevated bloodpressure is reached in the venous line, said closing means comprisingpressure-responsive control means adjustable to maintain the closure ofthe venous line independent of time; means for opening the venous lineand essentially simultaneously closing the arterial line, said openingmeans comprising time-responsive control means adjustable to maintainthe venous line open independent of pressure in the line for apredetermined time increment to inject the blood under pressure to thepatient, the duration of the closure of the arterial line being lessthan the duration of the venous line closure.
 4. A system forcontrolling the dialysis of blood comprising an arterial line conductingblood away from a patient, a venous line conducting blood toward thepatient, and a dialyzer situated between the arterial line and thevenous line, the improvement comprising: means for pumping bloodunidirectionally from the patient through the open arterial line at apressure which will not collapse blood-conducting conduit; means forclosing the venous line while the blood is being pumped, said closingmeans comprising a first independently variable control meansmaintaining closure of the venous line until a predetermined bloodpressure is reached in the system; means for opening the venous line andessentially simultaneously closing the arterial line, said opening meanscomprising a second independently variable control means allowingaccumulated pressure of the blood to inject the blood to the patient fora predetermined time increment, the duration of the closure of thearterial line being greater than the duration of the venous lineclosure.